China and Pakistan reached a formal agreement last month to construct a third nuclear reactor at Chashma that the Obama administration says will violate Beijing’s promises under an international anti-nuclear weapons accord.

According to U.S. intelligence and diplomatic officials, the secret agreement for the Chashma 3 reactor was signed in Beijing during the visit by a delegation from the Pakistan Atomic Energy Commission from Feb. 15 to 18.

The agreement calls for the state-run China National Nuclear Corp. to construct a 1,000-megawatt power plant at Chashma, located in the northern province of Punjab, where two earlier Chinese reactors were built.

China’s government last month issued an internal notice to officials within its nuclear establishment and to regional political leaders urging care to avoid any leaks of information about the nuclear sale that Beijing expects will be controversial, officials told the Washington Free Beacon, speaking on condition of anonymity.

The reactor deal had been in the works for several years and prompted high-level U.S. government efforts to block the sale because of concerns it will boost Pakistan’s nuclear weapons program.